1 00:00:00 --> 00:00:01 2 00:00:01 --> 00:00:03 The following content is provided by MIT OpenCourseWare 3 00:00:03 --> 00:00:06 under a Creative Commons license. 4 00:00:06 --> 00:00:09 Additional information about our license and 5 00:00:09 --> 00:00:10 MIT OpenCourseWare in 6 00:00:10 --> 00:00:15 general is available at ocw.mit.edu. 7 00:00:15 --> 00:00:23 PROFESSOR: This is the lecture on sleep and dreams, and you 8 00:00:23 --> 00:00:28 want to know about this because it's -- well, at MIT, sleep and 9 00:00:28 --> 00:00:31 dreams is a topic that falls under the heading of 10 00:00:31 --> 00:00:35 abnormal psychology. 11 00:00:35 --> 00:00:40 All right, let us ask to begin, how many people here got 12 00:00:40 --> 00:00:44 some sleep last night? 13 00:00:44 --> 00:00:45 OK. 14 00:00:45 --> 00:00:51 Of those people, how many people went to sleep, even 15 00:00:51 --> 00:00:57 though they knew they still had stuff they wanted to get done? 16 00:00:57 --> 00:00:57 All right. 17 00:00:57 --> 00:01:01 So, what's your problem? 18 00:01:01 --> 00:01:05 Well, the typical MIT answer to that is sort 19 00:01:05 --> 00:01:07 of a moral argument. 20 00:01:07 --> 00:01:09 I'm weak. 21 00:01:09 --> 00:01:13 I'm a miserable human being. 22 00:01:13 --> 00:01:18 If I was a good, strong human being, I would not have gotten 23 00:01:18 --> 00:01:22 sleep, I would have done that problem set and so on. 24 00:01:22 --> 00:01:28 25 00:01:28 --> 00:01:37 If you were not at MIT -- MIT is merely at one extreme here. 26 00:01:37 --> 00:01:42 Western civilization in general increasingly, since the 27 00:01:42 --> 00:01:47 invention of the lightbulb, has been an increasingly 28 00:01:47 --> 00:01:53 sleep-abusing, mechanism-abusing culture. 29 00:01:53 --> 00:01:56 But if you were left to your own devices or to what nature 30 00:01:56 --> 00:02:00 had intended, you'd be sleeping about eight hours a night, and 31 00:02:00 --> 00:02:05 you would be doing this across your life span with the result 32 00:02:05 --> 00:02:10 that you would spend about a third of your life asleep in 33 00:02:10 --> 00:02:13 this altered state of consciousness or 34 00:02:13 --> 00:02:13 unconsciousness. 35 00:02:13 --> 00:02:16 36 00:02:16 --> 00:02:21 That, if you're teaching a course on human behavior and 37 00:02:21 --> 00:02:26 human mental life, that requires some explanation. 38 00:02:26 --> 00:02:28 Why do people sleep? 39 00:02:28 --> 00:02:35 What is the nature of that behavior left 40 00:02:35 --> 00:02:36 to its normal state? 41 00:02:36 --> 00:02:39 What happens when you abuse it? 42 00:02:39 --> 00:02:43 Why do people dream, which is psychologically, perhaps, the 43 00:02:43 --> 00:02:46 most interesting piece of sleep. 44 00:02:46 --> 00:02:50 Is it possible to get any -- do those dreams, do those weird 45 00:02:50 --> 00:02:52 stories have any meaning? 46 00:02:52 --> 00:02:54 Those are the questions that I'll talk about. 47 00:02:54 --> 00:02:58 I don't know if I'll get to end of it today, otherwise I'll 48 00:02:58 --> 00:03:02 pick up after Thanksgiving. 49 00:03:02 --> 00:03:08 Let's talk initially about why and how you sleep. 50 00:03:08 --> 00:03:11 Well, look, I mean one level of answer would be you sleep 51 00:03:11 --> 00:03:18 because every so often nuclei, collections of nerve cells deep 52 00:03:18 --> 00:03:24 down in your brain stem send volleys of signals up to the 53 00:03:24 --> 00:03:26 rest of your brain that basically make like a 54 00:03:26 --> 00:03:28 hammer and knock you out. 55 00:03:28 --> 00:03:31 But that's not a deeply satisfying answer. 56 00:03:31 --> 00:03:37 It does point to the fact that it's a very basic drive, and 57 00:03:37 --> 00:03:38 it's a very powerful drive. 58 00:03:38 --> 00:03:45 Look, if you wanted to you could, for example, as a 59 00:03:45 --> 00:03:52 statement of extreme political conviction, sit right here and 60 00:03:52 --> 00:03:55 starve yourself to death. 61 00:03:55 --> 00:03:57 Hunger is an important drive. 62 00:03:57 --> 00:03:59 There are several people illustrating that at 63 00:03:59 --> 00:04:03 this very moment. 64 00:04:03 --> 00:04:08 If you wanted, you could override that and not eat, 65 00:04:08 --> 00:04:11 even to the point of killing yourself. 66 00:04:11 --> 00:04:16 That's not true, for example, about your breathing. 67 00:04:16 --> 00:04:19 If you wanted to sit here and hold your breath until you 68 00:04:19 --> 00:04:23 died, it wouldn't work. 69 00:04:23 --> 00:04:27 You may have tried this when you were little. 70 00:04:27 --> 00:04:30 One of my two sisters used to be a fan of this. 71 00:04:30 --> 00:04:33 If we were teasing her and chasing her she would just hold 72 00:04:33 --> 00:04:38 her breath until she keeled over, which was very dramatic, 73 00:04:38 --> 00:04:41 but not, in fact, life threatening, except in indirect 74 00:04:41 --> 00:04:44 sense that my mother was not thrilled with us making my 75 00:04:44 --> 00:04:46 little sister pass out. 76 00:04:46 --> 00:04:49 77 00:04:49 --> 00:04:51 You could ask her, she'll be here tomorrow, but 78 00:04:51 --> 00:04:52 you'll all be leaving. 79 00:04:52 --> 00:05:03 Anyway, this drive to sleep is more like the need 80 00:05:03 --> 00:05:06 to breath than the need to eat in that sense. 81 00:05:06 --> 00:05:10 If you were to sit here and by an act of will declare I will 82 00:05:10 --> 00:05:14 not fall asleep -- and look, as you well know, there's a 83 00:05:14 --> 00:05:17 substantial number of you who can't manage to do that 84 00:05:17 --> 00:05:19 for an hour and a half. 85 00:05:19 --> 00:05:22 That has to do with how you're abusing the normal mechanism on 86 00:05:22 --> 00:05:30 -- when I first was teaching, I used to look out at 10250 full 87 00:05:30 --> 00:05:33 of intro psych students in they're ahh. 88 00:05:33 --> 00:05:35 I'm thinking I'm not being lively enough here. 89 00:05:35 --> 00:05:38 I realize at this point, I could be setting off large 90 00:05:38 --> 00:05:41 explosions on a regular basis and it wouldn't matter 91 00:05:41 --> 00:05:43 for some people. 92 00:05:43 --> 00:05:45 We'll get to that in a minute. 93 00:05:45 --> 00:05:51 But even those of you who are well-rested, you could not 94 00:05:51 --> 00:05:53 sit here and not sleep. 95 00:05:53 --> 00:05:56 Probably you couldn't make it for twenty-four hours. 96 00:05:56 --> 00:05:59 Absolutely you could not make it for forty-eight hours 97 00:05:59 --> 00:06:05 without external help, either from drugs, like caffeine, or 98 00:06:05 --> 00:06:07 more particularly from somebody smacking you 99 00:06:07 --> 00:06:09 around to keep you awake. 100 00:06:09 --> 00:06:13 If you're in a sleep lab and you want to keep somebody awake 101 00:06:13 --> 00:06:20 for thirty-six hours or something to see what happens, 102 00:06:20 --> 00:06:23 you sure don't say, I'll give you ten bucks if you can 103 00:06:23 --> 00:06:24 stay awake all night. 104 00:06:24 --> 00:06:28 You need somebody there to slap them around and keep them 105 00:06:28 --> 00:06:30 moving or they'll be out. 106 00:06:30 --> 00:06:33 There's just no way to suppress that. 107 00:06:33 --> 00:06:37 It's a very, very powerful drive. 108 00:06:37 --> 00:06:40 So, how come? 109 00:06:40 --> 00:06:42 What's doing this? 110 00:06:42 --> 00:06:49 Your need to sleep is driven by two primary factors. 111 00:06:49 --> 00:06:51 One of them is a so-called circadian rhythm. 112 00:06:51 --> 00:06:55 The term comes from -- circadian is about a day, 113 00:06:55 --> 00:06:58 because it's a rhythm with a periodicity of about 114 00:06:58 --> 00:07:01 twenty-four hours. 115 00:07:01 --> 00:07:06 If you manage to measure it in isolation, and you were to 116 00:07:06 --> 00:07:09 measure something like alertness, it would have a 117 00:07:09 --> 00:07:13 roughly sinusoidal shape to it, this particular drive. 118 00:07:13 --> 00:07:18 When you wake up, it's actually at a relative low point. 119 00:07:18 --> 00:07:19 Yeah, right. 120 00:07:19 --> 00:07:23 At six a.m. on this chart, is it a relative low point? 121 00:07:23 --> 00:07:29 It rises your alertness driven by the circadian clock, rises 122 00:07:29 --> 00:07:33 systematically during the course of the day till early 123 00:07:33 --> 00:07:37 evening, and then declines to a nadir around four or 124 00:07:37 --> 00:07:39 five in the morning. 125 00:07:39 --> 00:07:43 When you're trying to stay up all night, that time in the wee 126 00:07:43 --> 00:07:46 hours of the morning when it's just really, really tough and 127 00:07:46 --> 00:07:53 you're getting the shakes and all, is when this circadian 128 00:07:53 --> 00:07:57 clock is crashing, is hitting its minimum. 129 00:07:57 --> 00:07:58 How do we measure this? 130 00:07:58 --> 00:08:00 How do we measure circadian cycles? 131 00:08:00 --> 00:08:04 Well, if you're a mouse it's actually relatively easy. 132 00:08:04 --> 00:08:06 Stick a mouse in a cage with one of those little running 133 00:08:06 --> 00:08:12 wheels and put a sensor on the running wheel, and you'll get 134 00:08:12 --> 00:08:15 out a graph that looks like the graph that I put 135 00:08:15 --> 00:08:16 on the handout. 136 00:08:16 --> 00:08:21 Each of the lines on that graph is one day, so you've got a day 137 00:08:21 --> 00:08:26 here, and the mouse is doing nothing much. 138 00:08:26 --> 00:08:29 Then at a certain point, the mouse jumps on the 139 00:08:29 --> 00:08:31 wheel and does stuff. 140 00:08:31 --> 00:08:36 Now, the convention of the circadian trade is to 141 00:08:36 --> 00:08:37 double-plot their data. 142 00:08:37 --> 00:08:42 So the line is the same data plotted twice. 143 00:08:42 --> 00:08:44 It's just makes it easier to see trends over the day. 144 00:08:44 --> 00:08:48 So this is inactivity, activity, same day. 145 00:08:48 --> 00:08:51 146 00:08:51 --> 00:08:55 This is twenty-four hours. 147 00:08:55 --> 00:09:06 You can see that the mouse does this every day, for day after 148 00:09:06 --> 00:09:10 day, like clockwork, as it were, because the mouse 149 00:09:10 --> 00:09:12 has this little clock that's telling it. 150 00:09:12 --> 00:09:18 Now, the point at which the mouse is firing things up, 151 00:09:18 --> 00:09:24 right about here, is the mouse was on a twelve hour light/dark 152 00:09:24 --> 00:09:26 schedule, and when the lights go out, the mouse turns on. 153 00:09:26 --> 00:09:28 It's a nocturnal beastie. 154 00:09:28 --> 00:09:32 When the lights go out he jumps on the wheel and goes berserk. 155 00:09:32 --> 00:09:37 Now, what happens halfway down that graph where there's an 156 00:09:37 --> 00:09:41 arrow pointing at the side of the data, at that point you 157 00:09:41 --> 00:09:44 leave the lights on continuously. 158 00:09:44 --> 00:09:50 What you discover is the mouse still behaves in a very 159 00:09:50 --> 00:09:51 systematic fashion. 160 00:09:51 --> 00:09:53 I'm not going to bother double-plotting my 161 00:09:53 --> 00:09:55 data anymore here. 162 00:09:55 --> 00:10:02 But now the period is starting to drift. 163 00:10:02 --> 00:10:06 The mouse is now doing what's known as free-running, and this 164 00:10:06 --> 00:10:13 is a way that you can take a look at the circadian cycle in 165 00:10:13 --> 00:10:16 this beastie because he's now no longer got the light signal 166 00:10:16 --> 00:10:19 telling him what time it is. 167 00:10:19 --> 00:10:22 What you discover is that it's advancing by about thirty 168 00:10:22 --> 00:10:28 minutes a day, because the mouse clock has a period, a 169 00:10:28 --> 00:10:31 circadian period of about twenty-three and a half hours 170 00:10:31 --> 00:10:35 -- not quite twenty-four hours. 171 00:10:35 --> 00:10:38 If you were in the same experiment and you were 172 00:10:38 --> 00:10:42 inclined to run around in a wheel, the day would actually 173 00:10:42 --> 00:10:46 go this way a little bit, because the human clock has a 174 00:10:46 --> 00:10:50 period of about twenty-four and a quarter to twenty-four and a 175 00:10:50 --> 00:10:51 half hours, some variation. 176 00:10:51 --> 00:10:55 It's again, around a day. 177 00:10:55 --> 00:11:01 It gets synchronized to the real day by 178 00:11:01 --> 00:11:03 light most strongly. 179 00:11:03 --> 00:11:06 So you know when it's morning because that's 180 00:11:06 --> 00:11:08 when the sun comes up. 181 00:11:08 --> 00:11:11 If you never get outside and you live in constant light, 182 00:11:11 --> 00:11:14 your clock may be drifting too in something fashion. 183 00:11:14 --> 00:11:18 But given a normal exposure to light/dark cycles, 184 00:11:18 --> 00:11:20 that sets the clock. 185 00:11:20 --> 00:11:23 How many people are flying across time zones to 186 00:11:23 --> 00:11:25 the next few days? 187 00:11:25 --> 00:11:29 So you guys are all going to be jet lagged in some fashion, 188 00:11:29 --> 00:11:33 because your clock is set for East coast, U.S., you'll 189 00:11:33 --> 00:11:35 go someplace else. 190 00:11:35 --> 00:11:38 Get outside because it's exposure to the sun 191 00:11:38 --> 00:11:40 that will reset you. 192 00:11:40 --> 00:11:42 Exposure to these sort of lights will reset you too, 193 00:11:42 --> 00:11:46 but the sun is sufficiently brighter that it makes 194 00:11:46 --> 00:11:49 a bigger difference. 195 00:11:49 --> 00:11:52 This clock, by the way, has a home. 196 00:11:52 --> 00:12:05 It's located in the suprachiasmatic nucleus. 197 00:12:05 --> 00:12:07 Looks more complicated than it is. 198 00:12:07 --> 00:12:10 Supra for above. 199 00:12:10 --> 00:12:16 Chiasmatic for the optic chiasm, that x where the optic 200 00:12:16 --> 00:12:21 nerves cross on the way from the eyes to the brain. 201 00:12:21 --> 00:12:24 This sits right on top of that and gets direct 202 00:12:24 --> 00:12:25 input from the retina. 203 00:12:25 --> 00:12:29 It's got its own visual system in a sense. 204 00:12:29 --> 00:12:33 How do we know that this is where the clock lives? 205 00:12:33 --> 00:12:34 There are a number of ways. 206 00:12:34 --> 00:12:37 But the coolest way that we know that this is where the 207 00:12:37 --> 00:12:43 clock lives is that there are clock mutants out there, 208 00:12:43 --> 00:12:46 probably some human, but certainly mouse mutants. 209 00:12:46 --> 00:12:50 Suppose you got a mouse mutant who, let's say, has a clock 210 00:12:50 --> 00:12:55 running at, say, twenty-two hours or something like that. 211 00:12:55 --> 00:12:59 You can go in, take out the suprachiasmatic nucleus from 212 00:12:59 --> 00:13:04 that mouse, put it into another mouse -- and this is a case 213 00:13:04 --> 00:13:06 where a brain transplant will actually work. 214 00:13:06 --> 00:13:11 The recipient mouse will now start running with the clock 215 00:13:11 --> 00:13:15 timing of the donor mouse. 216 00:13:15 --> 00:13:19 If you want a new clock, you can actually go and get -- I 217 00:13:19 --> 00:13:23 don't know if you go and get one from a mouse, and probably 218 00:13:23 --> 00:13:24 your neighbor doesn't want to donate. 219 00:13:24 --> 00:13:28 220 00:13:28 --> 00:13:30 There are also other clocks, by the way, that live in places 221 00:13:30 --> 00:13:37 like your liver, but the main clock running your behavior is 222 00:13:37 --> 00:13:40 sitting up there in your brain and reset by light, and in 223 00:13:40 --> 00:13:45 fact, can be transplanted, apparently. 224 00:13:45 --> 00:13:51 Now, humans don't tend to run in little mouse 225 00:13:51 --> 00:13:54 wheels very much. 226 00:13:54 --> 00:13:59 If you want to measure this in a human, if you stick a human 227 00:13:59 --> 00:14:06 in continuous light, and cut them off from the external 228 00:14:06 --> 00:14:08 world, which you can get yourself paid to 229 00:14:08 --> 00:14:09 do if you want. 230 00:14:09 --> 00:14:13 One of the leading sleep labs in the world, actually, 231 00:14:13 --> 00:14:17 is across the river at Brigham and Women's. 232 00:14:17 --> 00:14:20 My lab actually does some collaborating with them. 233 00:14:20 --> 00:14:22 So if you're interested talk to me. 234 00:14:22 --> 00:14:23 People do this as a summer job. 235 00:14:23 --> 00:14:28 You get locked in the lab for the summer. 236 00:14:28 --> 00:14:30 People think oh, I'm going to write the great American novel 237 00:14:30 --> 00:14:34 or something like that while I stay up all night or something. 238 00:14:34 --> 00:14:36 But you get paid a decent rate for this. 239 00:14:36 --> 00:14:42 240 00:14:42 --> 00:14:44 Now we're going to want to keep track of what your 241 00:14:44 --> 00:14:47 circadian clock is doing. 242 00:14:47 --> 00:14:50 The sorts of things that vary with your clock are, for 243 00:14:50 --> 00:14:53 example, body temperature. 244 00:14:53 --> 00:14:58 Your body temperature has about a one degree plus and minus 245 00:14:58 --> 00:15:01 swing with the circadian clock. 246 00:15:01 --> 00:15:05 So, if you've got a fever, for example, you'd probably 247 00:15:05 --> 00:15:07 remember from when you were a little kid that your fever 248 00:15:07 --> 00:15:10 would peak in the early evening. 249 00:15:10 --> 00:15:12 If you stay up all night it's four in the morning where 250 00:15:12 --> 00:15:14 you suddenly feel chilled. 251 00:15:14 --> 00:15:16 That's because your body temperature is actually 252 00:15:16 --> 00:15:19 varying as a function of the circadian cycle. 253 00:15:19 --> 00:15:23 There are lots of circulating hormones, like melatonin and 254 00:15:23 --> 00:15:27 others, in the blood that also track the circadian clock. 255 00:15:27 --> 00:15:32 So, if you're in the lab, somebody is going to be 256 00:15:32 --> 00:15:36 monitoring these various aspects of your physiology in 257 00:15:36 --> 00:15:39 an effort to take a look at where your circadian clock is. 258 00:15:39 --> 00:15:41 This is one of the things that sort of discourages people from 259 00:15:41 --> 00:15:45 immediately signing up, because well, for instance, if you're 260 00:15:45 --> 00:15:48 going to be taking continuous measures of body temperature, 261 00:15:48 --> 00:15:50 the thermometer is not under your tongue. 262 00:15:50 --> 00:15:54 263 00:15:54 --> 00:15:59 It's a slow group. 264 00:15:59 --> 00:16:10 Anyway, so you got the circadian clock that's 265 00:16:10 --> 00:16:13 driving your alertness. 266 00:16:13 --> 00:16:17 The other piece that's driving you're alertness, or inversely 267 00:16:17 --> 00:16:23 this powerful drive to sleep, is sometimes called the 268 00:16:23 --> 00:16:23 sleep homeostatic. 269 00:16:23 --> 00:16:26 It's simply a homeostatic mechanism that says the 270 00:16:26 --> 00:16:31 longer you're awake, the more tired you get. 271 00:16:31 --> 00:16:34 This is not a huge surprise. 272 00:16:34 --> 00:16:35 So we can graph that here. 273 00:16:35 --> 00:16:37 So this again, alertness. 274 00:16:37 --> 00:16:40 Let's say this is 6:00 a.m. again, now let's say that you 275 00:16:40 --> 00:16:44 wake up at something like 8:00, and basically it's a roughly 276 00:16:44 --> 00:16:49 linear function of during the day you get sleepier and 277 00:16:49 --> 00:16:50 sleepier and sleepier and sleepier, and sleepier, 278 00:16:50 --> 00:16:51 and sleepier. 279 00:16:51 --> 00:16:53 This thing builds up pressure to sleep. 280 00:16:53 --> 00:16:57 If you now go to sleep at let's say 11:00, that recovers. 281 00:16:57 --> 00:17:01 It recovers at least initially rather steeply, and 282 00:17:01 --> 00:17:03 then probably has 283 00:17:03 --> 00:17:04 a sort of an exponential tail. 284 00:17:04 --> 00:17:09 It's not absolutely clear. 285 00:17:09 --> 00:17:15 But if you combine these two, well, if you were to combine 286 00:17:15 --> 00:17:20 these two in the way that nature intended, what you get 287 00:17:20 --> 00:17:26 is a sustained period of -- let's look at the 288 00:17:26 --> 00:17:27 course of the day. 289 00:17:27 --> 00:17:33 Suppose you wake up in the relatively early morning, your 290 00:17:33 --> 00:17:39 circadian clock is relatively depressed, so it's still 291 00:17:39 --> 00:17:41 feeling kind of sleepy. 292 00:17:41 --> 00:17:46 But you're homeostat is fully refreshed, so you're up here, 293 00:17:46 --> 00:17:49 let's say, in alertness land. 294 00:17:49 --> 00:17:53 Now as the homeostat is going down, the 295 00:17:53 --> 00:17:56 circadian chunk is going up. 296 00:17:56 --> 00:17:59 So for a sustained period of the day, say till early 297 00:17:59 --> 00:18:04 evening, you have roughly level alertness. 298 00:18:04 --> 00:18:07 Believe it or not, that's what really happens to people 299 00:18:07 --> 00:18:08 who are well-rested. 300 00:18:08 --> 00:18:11 They are awake during the day. 301 00:18:11 --> 00:18:13 302 00:18:13 --> 00:18:24 Some time in early evening when the circadian clock turns 303 00:18:24 --> 00:18:28 downward, things start going downhill for you and 304 00:18:28 --> 00:18:32 your alertness starts steadily dropping. 305 00:18:32 --> 00:18:38 At some point it drops enough that you -- well, that people 306 00:18:38 --> 00:18:43 who are not abusing the system -- go to sleep. 307 00:18:43 --> 00:18:47 308 00:18:47 --> 00:18:52 So now, you're asleep so you're not terribly alert. 309 00:18:52 --> 00:18:56 So what's happening now is, so you're down here in asleep land 310 00:18:56 --> 00:19:01 somewhere, now your homeostat is recovering, right? 311 00:19:01 --> 00:19:05 But in the early portions of your sleep, or during the 312 00:19:05 --> 00:19:06 course of the night, this circadian thing is 313 00:19:06 --> 00:19:08 still crashing down. 314 00:19:08 --> 00:19:12 So even though you may have climbed up here already on the 315 00:19:12 --> 00:19:17 homeostat, you're crashing down to here and the circadian thing 316 00:19:17 --> 00:19:21 is saying stay asleep, stay asleep, it's good for you. 317 00:19:21 --> 00:19:26 You should be asleep for this sustained eight hours. 318 00:19:26 --> 00:19:32 Then it turns around in the early morning hours and 319 00:19:32 --> 00:19:33 4:00, 5:00, 6:00 a.m. 320 00:19:33 --> 00:19:36 you wake with the chickens and you're bright and perky and 321 00:19:36 --> 00:19:40 alert, like you are every morning. 322 00:19:40 --> 00:19:41 You're back. 323 00:19:41 --> 00:19:44 So what you get out of this system, if it's being allowed 324 00:19:44 --> 00:19:49 to work properly, is a sustained period of alertness 325 00:19:49 --> 00:19:52 during the day, and the sustained bout of sleep 326 00:19:52 --> 00:19:53 during the night. 327 00:19:53 --> 00:19:59 If you crash the circadian system, for instance, you 328 00:19:59 --> 00:20:03 end up with broken sleep. 329 00:20:03 --> 00:20:10 So, you blow up a mouse's circadian clock, and what you 330 00:20:10 --> 00:20:13 get is a mouse who runs and naps, and runs and naps, and 331 00:20:13 --> 00:20:19 runs and naps -- doesn't have this organized pattern to it. 332 00:20:19 --> 00:20:24 Now, the great tragedy, of course, is that you guys who 333 00:20:24 --> 00:20:31 are in the peak of your ability to do this aren't doing it. 334 00:20:31 --> 00:20:34 You're abusing the pants off it. 335 00:20:34 --> 00:20:38 The structure of sleep changes over the course 336 00:20:38 --> 00:20:40 of the lifespan. 337 00:20:40 --> 00:20:45 Babies sleep for a lot longer than adults do. 338 00:20:45 --> 00:20:50 After early childhood, people have a fairly constant 339 00:20:50 --> 00:20:52 requirement for about eight hours. 340 00:20:52 --> 00:20:55 The range is really about seven to nine hours. 341 00:20:55 --> 00:21:01 People who say they require only four hours of sleep or 342 00:21:01 --> 00:21:04 something like that are basically lying to you. 343 00:21:04 --> 00:21:06 344 00:21:06 --> 00:21:09 Thomas Edison, right, he's always trotted out 345 00:21:09 --> 00:21:10 as the example here. 346 00:21:10 --> 00:21:12 I don't remember what he needed, two hours a night, 347 00:21:12 --> 00:21:13 four hours a night. 348 00:21:13 --> 00:21:17 Well, there was a reason the man had a cot in is office. 349 00:21:17 --> 00:21:20 The people who don't sleep eight hours at night are 350 00:21:20 --> 00:21:22 catching naps when they can and they're building up a sleep 351 00:21:22 --> 00:21:26 debt the rest of the time. 352 00:21:26 --> 00:21:36 The sleep debt is -- if you are Dement, William Dement, 353 00:21:36 --> 00:21:40 Stanford sleep researcher coined the term sleep debt, I 354 00:21:40 --> 00:21:43 think, argues that it may be the biggest health problem 355 00:21:43 --> 00:21:44 in the U.S. Why is that? 356 00:21:44 --> 00:21:48 Well because all sorts of stuff from traffic accidents to 357 00:21:48 --> 00:21:54 industrial accidents and so on, occur basically in the wee 358 00:21:54 --> 00:21:57 hours of the morning when the circadian clock is busy 359 00:21:57 --> 00:22:03 crashing, because sleepiness is not good for behavior, as 360 00:22:03 --> 00:22:07 you may have noticed in various and sundry ways. 361 00:22:07 --> 00:22:11 When you get older, it turns out to get harder -- for 362 00:22:11 --> 00:22:13 reasons we don't really understand -- to maintain this 363 00:22:13 --> 00:22:16 consolidated period of sleep. 364 00:22:16 --> 00:22:22 So, it is a sad fact that I, for instance, do not typically 365 00:22:22 --> 00:22:26 manage to sleep eight hours solidly, anything like eight 366 00:22:26 --> 00:22:31 hours solidly, at a stretch anymore, even though I have 367 00:22:31 --> 00:22:35 long ago abandoned my various efforts to abuse the system. 368 00:22:35 --> 00:22:37 I'd love to sleep a solid 369 00:22:37 --> 00:22:39 twelve, seven would be happy enough. 370 00:22:39 --> 00:22:42 But as you get older it's harder to maintain it. 371 00:22:42 --> 00:22:44 You can do it now and you're not doing it. 372 00:22:44 --> 00:22:46 It's so sad. 373 00:22:46 --> 00:22:49 So, what are you doing and why are you so deluded? 374 00:22:49 --> 00:22:54 Well, in part you're being deluded by this circadian 375 00:22:54 --> 00:22:57 clock, because what happens? 376 00:22:57 --> 00:23:00 You stay up all night, right. 377 00:23:00 --> 00:23:02 So, where should we plot this? 378 00:23:02 --> 00:23:03 What we don't have any colors. 379 00:23:03 --> 00:23:08 380 00:23:08 --> 00:23:12 Let's assume that you were once well-rested like before you 381 00:23:12 --> 00:23:19 arrived at MIT or something, and you stay up all night. 382 00:23:19 --> 00:23:21 So you were doing fine till here and now you're 383 00:23:21 --> 00:23:24 going to stay up. 384 00:23:24 --> 00:23:26 I'm getting sleepier here. 385 00:23:26 --> 00:23:30 Well, there's the coffee and the Jolt cola. 386 00:23:30 --> 00:23:34 387 00:23:34 --> 00:23:36 Who knows what else smacking you around. 388 00:23:36 --> 00:23:38 Stuff happens. 389 00:23:38 --> 00:23:42 But you know, you're fighting a losing battle here. 390 00:23:42 --> 00:23:46 At 4:00 in the morning and you're barely holding on, and 391 00:23:46 --> 00:23:49 let me tell you that psych paper that you're writing at 392 00:23:49 --> 00:23:51 that point is not your best work. 393 00:23:51 --> 00:23:54 394 00:23:54 --> 00:23:55 So there goes 4:00 in the morning. 395 00:23:55 --> 00:23:59 But 6:00, 7:00 in the morning, you've been up all night. 396 00:23:59 --> 00:24:00 What happens? 397 00:24:00 --> 00:24:04 The circadian clock turns around. 398 00:24:04 --> 00:24:11 I did it, I did it, I don't need your sleep, I'm so good. 399 00:24:11 --> 00:24:13 I'm a real MIT student! 400 00:24:13 --> 00:24:19 This is great, but it's all fake. 401 00:24:19 --> 00:24:21 You think you're getting back up here, forget it. 402 00:24:21 --> 00:24:22 You're in here somewhere. 403 00:24:22 --> 00:24:24 Klunk, like that. 404 00:24:24 --> 00:24:27 405 00:24:27 --> 00:24:31 So you're ambling around in this business. 406 00:24:31 --> 00:24:37 If you think that this is great evidence that I'm superman 407 00:24:37 --> 00:24:41 and I don't need to sleep, try it the second night. 408 00:24:41 --> 00:24:43 I don't know how many of you have ever tried staying 409 00:24:43 --> 00:24:44 awake two nights. 410 00:24:44 --> 00:24:49 The way to stay awake two nights in a row is to have 411 00:24:49 --> 00:24:53 somebody shooting at you. 412 00:24:53 --> 00:24:59 Leading funders of sleep research are Army and Airforce, 413 00:24:59 --> 00:25:01 and they have a very particular interest. 414 00:25:01 --> 00:25:04 Their interest is -- well, they have sort of two interests. 415 00:25:04 --> 00:25:08 One of the army interests is we're going to take over this 416 00:25:08 --> 00:25:11 country in a hundred hours straight and our boys ain't 417 00:25:11 --> 00:25:14 going to sleep until it's done, and we don't want 418 00:25:14 --> 00:25:18 any ill effects of this. 419 00:25:18 --> 00:25:21 Got some good drugs for us, we need drugs, we want good drugs. 420 00:25:21 --> 00:25:23 That's for the Army research program. 421 00:25:23 --> 00:25:27 The Airforce says, we can fly at night, this is cool, we've 422 00:25:27 --> 00:25:30 got really cool toys, we can fly at night. 423 00:25:30 --> 00:25:33 It's really bad when the helicopter guy falls 424 00:25:33 --> 00:25:39 asleep, so we need him to stay awake at bad times. 425 00:25:39 --> 00:25:43 So they're big time funders of this kind of stuff. 426 00:25:43 --> 00:25:49 It is the fact that the sort of thing -- your general level of 427 00:25:49 --> 00:25:53 arousal will keep you up, and so the panicked sense that 428 00:25:53 --> 00:25:55 you're going to flunk psych if you don't finish the 429 00:25:55 --> 00:25:57 paper will do some good. 430 00:25:57 --> 00:25:59 The panicked sense that if you fall asleep somebody's going to 431 00:25:59 --> 00:26:03 shoot you does a lot of good. 432 00:26:03 --> 00:26:08 You can stay awake for a long time under that basis. 433 00:26:08 --> 00:26:12 But it's not that you miraculously if you just 434 00:26:12 --> 00:26:15 can make it past here you get back up here. 435 00:26:15 --> 00:26:17 436 00:26:17 --> 00:26:20 This thing, if you don't keep recovering, it 437 00:26:20 --> 00:26:21 just keeps going. 438 00:26:21 --> 00:26:25 439 00:26:25 --> 00:26:27 Eventually you're going to fall asleep. 440 00:26:27 --> 00:26:33 It's just going to happen to you. 441 00:26:33 --> 00:26:39 So that's the broad sort of twenty-four hour 442 00:26:39 --> 00:26:41 scale of sleep. 443 00:26:41 --> 00:26:48 Within that, there's a structure on top of that. 444 00:26:48 --> 00:26:55 This is sort of a ninety minute ripple sitting on top of this 445 00:26:55 --> 00:27:02 circadian clock that runs all day and while you're asleep. 446 00:27:02 --> 00:27:07 You know this during the day by the variations -- what would 447 00:27:07 --> 00:27:10 you may have noticed were reliable fluctuations in your 448 00:27:10 --> 00:27:13 own alertness during the day. 449 00:27:13 --> 00:27:18 In fact, you can probably do this -- I should collect 450 00:27:18 --> 00:27:20 data on this some year. 451 00:27:20 --> 00:27:23 I'll have to make up a little questionnaire. 452 00:27:23 --> 00:27:25 The clock is about ninety minutes, this lecture's 453 00:27:25 --> 00:27:27 about ninety minutes. 454 00:27:27 --> 00:27:34 So sometime during this lecture, you'll hit the nadir 455 00:27:34 --> 00:27:37 of that ninety minute cycle. 456 00:27:37 --> 00:27:41 Actually, I can at least ask a general question. 457 00:27:41 --> 00:27:45 How many people think they could identify within plus or 458 00:27:45 --> 00:27:49 minus fifteen minutes the point during an average intro psych 459 00:27:49 --> 00:27:53 lecture where they're going, if they're going to lose is, where 460 00:27:53 --> 00:27:54 are they going to lose it? 461 00:27:54 --> 00:27:57 462 00:27:57 --> 00:28:01 Many of us know that there are just chunks 463 00:28:01 --> 00:28:03 of time that are bad. 464 00:28:03 --> 00:28:06 You might notice, if you check out, if you were to 465 00:28:06 --> 00:28:08 systematically survey those during the course of the day, 466 00:28:08 --> 00:28:10 of course, it interacts with things like when you eat your 467 00:28:10 --> 00:28:13 meals, when you get up, whether you ever got to sleep last 468 00:28:13 --> 00:28:17 night and things like that, but you may be able to peg a series 469 00:28:17 --> 00:28:20 of these spaced out at ninety minutes or maybe 180 minutes 470 00:28:20 --> 00:28:24 during the course of the day. 471 00:28:24 --> 00:28:26 You see these at night, too. 472 00:28:26 --> 00:28:36 473 00:28:36 --> 00:28:38 To talk about that let's fill out this cute little 474 00:28:38 --> 00:28:41 chart on the handout. 475 00:28:41 --> 00:28:44 476 00:28:44 --> 00:28:47 If I just stick a bunch of electrodes on your head and 477 00:28:47 --> 00:28:55 record the electroencephalogram the mass potentials off of 478 00:28:55 --> 00:29:01 billions of neurons in your brain, what I will see grossly 479 00:29:01 --> 00:29:06 is high frequency, low amplitude stuff while 480 00:29:06 --> 00:29:07 you are awake. 481 00:29:07 --> 00:29:12 So this is EEG. 482 00:29:12 --> 00:29:16 Depending on where I put my electrode in the brain -- on 483 00:29:16 --> 00:29:18 the scalp, rather, I can get a lot of other interesting 484 00:29:18 --> 00:29:19 information out of it. 485 00:29:19 --> 00:29:21 But for present purposes the important thing is that the 486 00:29:21 --> 00:29:25 mass activity of the brain is relatively high frequency, 487 00:29:25 --> 00:29:28 low amplitude stuff. 488 00:29:28 --> 00:29:35 If I now take a look at you when you are deeply asleep, 489 00:29:35 --> 00:29:42 what I will find is low frequency, high amplitude 490 00:29:42 --> 00:29:52 waves, roughly corresponding to -- what's going on is in deep 491 00:29:52 --> 00:29:56 sleep, large bodies of neurons are firing together -- 492 00:29:56 --> 00:29:59 everybody's on then everybody's off. 493 00:29:59 --> 00:30:04 If you're woken up out of that state, that's the I don't know 494 00:30:04 --> 00:30:08 where I am kind of state. 495 00:30:08 --> 00:30:12 You're deeply asleep here. 496 00:30:12 --> 00:30:15 The interesting thing, discovered now about fifty 497 00:30:15 --> 00:30:24 years ago, is that every ninety minutes or so you'll go into 498 00:30:24 --> 00:30:27 what we will call Rapid Eye Movement sleep for reasons that 499 00:30:27 --> 00:30:31 will be apparently in the next line of this table, where all 500 00:30:31 --> 00:30:37 of a sudden the brain goes back to this high frequency, low 501 00:30:37 --> 00:30:41 amplitude kind of signal. 502 00:30:41 --> 00:30:44 Now, research over the course of the fifty years makes it 503 00:30:44 --> 00:30:47 clear this is not exactly the same as this, but it 504 00:30:47 --> 00:30:50 certainly looks awake-like. 505 00:30:50 --> 00:30:52 So the person is still clearly asleep. 506 00:30:52 --> 00:30:55 The interesting thing is if you wake somebody up out of this 507 00:30:55 --> 00:30:58 state, they will reliably report that they are dreaming. 508 00:30:58 --> 00:31:00 Not all the time. 509 00:31:00 --> 00:31:02 If you wake people up out of this state, they will 510 00:31:02 --> 00:31:05 reliably report that they are not dreaming. 511 00:31:05 --> 00:31:07 Again, not all the time. 512 00:31:07 --> 00:31:09 It's not a perfect divide. 513 00:31:09 --> 00:31:12 But lots of narrative dreaming here. 514 00:31:12 --> 00:31:15 Here you tend to get if you wake people up and say what was 515 00:31:15 --> 00:31:19 going on, you might get an isolated thought or some idea 516 00:31:19 --> 00:31:22 that was rattling around, but you won't get that I was flying 517 00:31:22 --> 00:31:25 naked through the infinite corridor with a panda on 518 00:31:25 --> 00:31:27 my back or something. 519 00:31:27 --> 00:31:29 We'll talk about that later. 520 00:31:29 --> 00:31:34 521 00:31:34 --> 00:31:42 This is the nighttime manifestation of that ninety 522 00:31:42 --> 00:31:46 minute cycle that you also see running during the 523 00:31:46 --> 00:31:47 course of the day. 524 00:31:47 --> 00:31:50 You can pick that up in the movements of the eyes, too. 525 00:31:50 --> 00:31:52 That's the electro-oculogram. 526 00:31:52 --> 00:32:03 While you are awake, your eyes move ballistically to the 527 00:32:03 --> 00:32:05 left and to the right. 528 00:32:05 --> 00:32:09 Your eyes are sitting in one place then jumping someplace 529 00:32:09 --> 00:32:11 else and moving around like so. 530 00:32:11 --> 00:32:14 The two eyes are moving together, so-called 531 00:32:14 --> 00:32:17 consensual eye movement. 532 00:32:17 --> 00:32:23 In deep sleep, those ballistic movements, called saccades, 533 00:32:23 --> 00:32:28 disappear and the consensual movements are damped down to so 534 00:32:28 --> 00:32:33 the eyes are kind of rolling around in your head and they're 535 00:32:33 --> 00:32:35 not necessarily rolling in that same place. 536 00:32:35 --> 00:32:38 537 00:32:38 --> 00:32:42 When you go into Rapid Eye Movement sleep, the reason it 538 00:32:42 --> 00:32:44 was called Rapid Eye Movement sleep, it's the eyes look 539 00:32:44 --> 00:32:46 like they're awake again. 540 00:32:46 --> 00:32:54 So again, ballistically jumping around and jumping together. 541 00:32:54 --> 00:32:58 Is the pattern of eye movements related to what's going 542 00:32:58 --> 00:33:00 on in your dream? 543 00:33:00 --> 00:33:02 Well, there's anecdotal evidence for it, but if you 544 00:33:02 --> 00:33:05 think about it it's very difficult to do the experiment 545 00:33:05 --> 00:33:08 in any terribly meaningful -- actually there's some 546 00:33:08 --> 00:33:13 interesting data in animals at this point. 547 00:33:13 --> 00:33:17 In any case, the eyes look like they're awake here. 548 00:33:17 --> 00:33:20 The eyes, they're doing the same thing that they were 549 00:33:20 --> 00:33:22 doing when they were awake. 550 00:33:22 --> 00:33:28 You can see this in your roommate, particularly 551 00:33:28 --> 00:33:32 if your roommate has relatively thin lids. 552 00:33:32 --> 00:33:36 You can often see the eyes moving around under the lids, 553 00:33:36 --> 00:33:40 and if you watch your sleeping roommate, your sleeping 554 00:33:40 --> 00:33:43 roommate may think you're a weirdo when he or she wakes up. 555 00:33:43 --> 00:33:46 But you can actually see the eyes jerking 556 00:33:46 --> 00:33:50 around under the lids. 557 00:33:50 --> 00:33:54 558 00:33:54 --> 00:33:58 If you have an unusual roommate who sleeps with the eyes open 559 00:33:58 --> 00:34:01 -- this actually happens. 560 00:34:01 --> 00:34:05 The reason for sleeping with your eyes closed has less to 561 00:34:05 --> 00:34:08 do with -- it presumably has something to do with cutting 562 00:34:08 --> 00:34:11 the light out, but it had mostly to do with keeping the 563 00:34:11 --> 00:34:15 cornea hydrated, keeping it moist while you're asleep. 564 00:34:15 --> 00:34:19 If you sleep with your eyes open, you wake up with nasty, 565 00:34:19 --> 00:34:21 scratchy, itchy eyeballs. 566 00:34:21 --> 00:34:23 Because if you think about it, you don't sleep 567 00:34:23 --> 00:34:25 with your ears closed. 568 00:34:25 --> 00:34:29 It's perfectly possible to use your brain in some fashion to 569 00:34:29 --> 00:34:33 shut off enough of the ambient outside stimulus to go 570 00:34:33 --> 00:34:36 to sleep to get rid of the auditory stimulus. 571 00:34:36 --> 00:34:39 So, in principle, you can do that with your eyes too. 572 00:34:39 --> 00:34:42 But you close your eyes to keep them nice and moist. 573 00:34:42 --> 00:34:44 So some people that doesn't work terribly -- I traveled 574 00:34:44 --> 00:34:51 across France in a train with a guy who fell asleep but his 575 00:34:51 --> 00:34:55 eyes were open, and it's like traveling across France 576 00:34:55 --> 00:34:58 with the undead. 577 00:34:58 --> 00:35:02 Because at some point he went into REM sleep and his eyes 578 00:35:02 --> 00:35:06 were going all over the place, but he ain't looking at 579 00:35:06 --> 00:35:09 nothing that's there. 580 00:35:09 --> 00:35:12 It was a little strange. 581 00:35:12 --> 00:35:17 So, so far, awake and dreaming sleep look the same. 582 00:35:17 --> 00:35:21 583 00:35:21 --> 00:35:24 If you think you're having trouble telling whether your 584 00:35:24 --> 00:35:27 roommate's actually asleep, here's how you can tell. 585 00:35:27 --> 00:35:32 You measure muscle tone, electromyogram. 586 00:35:32 --> 00:35:36 When you are awake, your muscles are on, right. 587 00:35:36 --> 00:35:36 You have good muscle tone. 588 00:35:36 --> 00:35:39 That's why your head doesn't fall off of your shoulders 589 00:35:39 --> 00:35:43 and I can stand upright and stuff like that. 590 00:35:43 --> 00:35:49 When you are in deep sleep, actually your 591 00:35:49 --> 00:35:51 muscles remain on. 592 00:35:51 --> 00:35:52 The muscle tone remains high. 593 00:35:52 --> 00:35:58 It's when you go into REM sleep that you lose muscle tone. 594 00:35:58 --> 00:36:04 You can see this in your friendly neighborhood cat, 595 00:36:04 --> 00:36:08 because all this stuff shows up widely in mammalian species. 596 00:36:08 --> 00:36:12 So, your cat who's sleeping like this, that's a deeply 597 00:36:12 --> 00:36:16 sleeping cat whose muscle tone is doing just fine, thank you. 598 00:36:16 --> 00:36:20 Your cat who's sleeping like that is a cat who is in REM 599 00:36:20 --> 00:36:26 sleep and has lost muscle tone. 600 00:36:26 --> 00:36:32 Now, why would you turn the muscles off in REM sleep? 601 00:36:32 --> 00:36:35 602 00:36:35 --> 00:36:36 AUDIENCE: [INAUDIBLE PHRASE]. 603 00:36:36 --> 00:36:44 604 00:36:44 --> 00:36:44 PROFESSOR: Yeah. 605 00:36:44 --> 00:36:48 If you're busy being Superman and leaping tall buildings in a 606 00:36:48 --> 00:36:51 single bound in your dreams, it's a really good idea if you 607 00:36:51 --> 00:36:56 don't actually try that out. 608 00:36:56 --> 00:37:00 Not only are you protecting yourself, you're protecting 609 00:37:00 --> 00:37:03 anybody else you happen to be sleeping with. 610 00:37:03 --> 00:37:10 A known sleep disorder in older men is that this blockade of 611 00:37:10 --> 00:37:16 voluntary muscles fades off, and the result -- and this is a 612 00:37:16 --> 00:37:20 known disorder because older women bring the older men to 613 00:37:20 --> 00:37:24 the doctor, because their husband is thrashing around in 614 00:37:24 --> 00:37:28 the middle of the night and whacking her. 615 00:37:28 --> 00:37:31 This is a real problem, people get hurt. 616 00:37:31 --> 00:37:35 So, you want the muscles to go off. 617 00:37:35 --> 00:37:36 There are a number of corollaries here. 618 00:37:36 --> 00:37:43 It turns out that sleep walking -- Shakespeare has it wrong. 619 00:37:43 --> 00:37:47 Lady Macbeth is clearly dreaming about having murdered 620 00:37:47 --> 00:37:50 Duncan and all that when she's sleep walking. 621 00:37:50 --> 00:37:54 Typically, sleep walking is not acting out your dreams. 622 00:37:54 --> 00:38:01 It is a version of non-REM sleep, and it's much more 623 00:38:01 --> 00:38:04 typical in children than in adults. 624 00:38:04 --> 00:38:06 How many of you know that used to walk around at 625 00:38:06 --> 00:38:09 night when you were--? 626 00:38:09 --> 00:38:12 Little kids wandering around, their eyes are open, 627 00:38:12 --> 00:38:15 but nobody's home here. 628 00:38:15 --> 00:38:20 629 00:38:20 --> 00:38:22 I don't actually know that much about it. 630 00:38:22 --> 00:38:27 My theory is that part of what's doing this is it's your 631 00:38:27 --> 00:38:32 bladder telling you to get up and the rest of your brain's 632 00:38:32 --> 00:38:34 saying we want to stay asleep here. 633 00:38:34 --> 00:38:37 My theory is based on one of the great moments of 634 00:38:37 --> 00:38:44 child-rearing in my household, which was one of my children. 635 00:38:44 --> 00:38:48 We were awakened in the middle of the night, my wife and I, by 636 00:38:48 --> 00:38:56 one of my son's yelling "No, not here!" to the other son 637 00:38:56 --> 00:39:00 who was about to use a trash can for the wrong purpose. 638 00:39:00 --> 00:39:07 639 00:39:07 --> 00:39:09 Anyway, it all worked out in the end. 640 00:39:09 --> 00:39:11 641 00:39:11 --> 00:39:14 But this is a deep sleep phenomenon. 642 00:39:14 --> 00:39:24 Talking in your sleep is often, apparently, talking out of -- 643 00:39:24 --> 00:39:30 you're not going to hurt yourself too much if you don't 644 00:39:30 --> 00:39:35 blockade your jaw, right? 645 00:39:35 --> 00:39:39 It's the main body muscles that are the real threat. 646 00:39:39 --> 00:39:43 So sometimes people will end up talking in their sleep, often 647 00:39:43 --> 00:39:50 to the amusement of other people in the room, or to the 648 00:39:50 --> 00:39:54 inconvenience of other people, or of your own relationships, 649 00:39:54 --> 00:39:58 if what you're talking about is somebody else other than the 650 00:39:58 --> 00:40:01 person who's currently present with you. 651 00:40:01 --> 00:40:05 Anyway, it's not clear -- when we get to meaning of dreams 652 00:40:05 --> 00:40:06 we can talk about this. 653 00:40:06 --> 00:40:13 Anyway, so this is the sort of within the circadian 654 00:40:13 --> 00:40:19 cycle, this is the sort of structure you get in sleep. 655 00:40:19 --> 00:40:22 656 00:40:22 --> 00:40:26 Oh, now there's much more to this than what I'm telling you. 657 00:40:26 --> 00:40:31 Deep sleep can be subdivided into multiple stages that 658 00:40:31 --> 00:40:33 differ in the activity of different parts of 659 00:40:33 --> 00:40:37 your brain and so on. 660 00:40:37 --> 00:40:41 661 00:40:41 --> 00:40:46 So now between that twenty-four hour cycle and this ninety 662 00:40:46 --> 00:40:50 minute cycle, there is yet another level of structure to a 663 00:40:50 --> 00:40:56 night's sleep where there's more non-REM, slow wave, deep 664 00:40:56 --> 00:40:58 sleep early in the night. 665 00:40:58 --> 00:41:02 If you have a consolidated bout of eight hours of sleep, a 666 00:41:02 --> 00:41:06 normal night's sleep, what you will see is more of this stuff 667 00:41:06 --> 00:41:11 early in the night and more of this stuff later in the night. 668 00:41:11 --> 00:41:14 This is accompanied by systematic changes in the 669 00:41:14 --> 00:41:19 neurochemistry of the sleeping brain and so on. 670 00:41:19 --> 00:41:23 There's an intermediate level of structure to sleep also. 671 00:41:23 --> 00:41:30 The impression one gets is of a beautifully structured system 672 00:41:30 --> 00:41:35 that is designed to do something. 673 00:41:35 --> 00:41:40 So, I mean apart from the obvious, it's designed to keep 674 00:41:40 --> 00:41:44 you from feeling sleepy. 675 00:41:44 --> 00:41:52 One wants to know, well, what is sleep for? 676 00:41:52 --> 00:41:56 You'd be surprised if a third of your life is spent in this 677 00:41:56 --> 00:41:58 state for no good reason. 678 00:41:58 --> 00:42:04 Oh, look at that, it says Part Two: Why do we sleep? 679 00:42:04 --> 00:42:08 It suggests that there are several possible reasons here. 680 00:42:08 --> 00:42:11 Anybody care to offer any possible series 681 00:42:11 --> 00:42:13 of why we sleep? 682 00:42:13 --> 00:42:17 683 00:42:17 --> 00:42:18 Nobody's got a clue. 684 00:42:18 --> 00:42:20 Yes? 685 00:42:20 --> 00:42:28 AUDIENCE: [INAUDIBLE] 686 00:42:28 --> 00:42:31 PROFESSOR: So there's a sort of a basic rest and 687 00:42:31 --> 00:42:33 regeneration notion. 688 00:42:33 --> 00:42:37 That you use your muscles all day, it builds up all those 689 00:42:37 --> 00:42:41 metabolic byproducts in muscles that you learned about 690 00:42:41 --> 00:42:42 once upon a time. 691 00:42:42 --> 00:42:47 Sleep/rest will give you a chance to clear that out. 692 00:42:47 --> 00:42:50 So certainly, one possibility is it's an enforced 693 00:42:50 --> 00:42:50 rest period. 694 00:42:50 --> 00:42:54 You could enforce rest some other way, presumably. 695 00:42:54 --> 00:42:58 Well, it could be good for you to rest, period -- just 696 00:42:58 --> 00:42:59 lie around and do nothing. 697 00:42:59 --> 00:43:02 But sleep kind of enforces that. 698 00:43:02 --> 00:43:03 Yes, there was a hand over there somewhere. 699 00:43:03 --> 00:43:07 AUDIENCE: [INAUDIBLE] 700 00:43:07 --> 00:43:10 PROFESSOR: So, there's a whole class of theories, and these 701 00:43:10 --> 00:43:15 are actually the ones where there's, I suppose, the most 702 00:43:15 --> 00:43:18 current interest that has to do with learning and memory. 703 00:43:18 --> 00:43:25 That somehow what sleep is about is tuning up your 704 00:43:25 --> 00:43:29 memories and you're consolidating memories, 705 00:43:29 --> 00:43:32 improving learning or something like that. 706 00:43:32 --> 00:43:33 Let's talk more about that in a minute. 707 00:43:33 --> 00:43:36 But if you're sitting there saying, I'm a real MIT student, 708 00:43:36 --> 00:43:37 I don't need to sleep. 709 00:43:37 --> 00:43:41 You might worry about theories that say sleep is vital to 710 00:43:41 --> 00:43:44 the consolidation of memory. 711 00:43:44 --> 00:43:44 Yeah? 712 00:43:44 --> 00:43:45 AUDIENCE: It's 713 00:43:45 --> 00:43:48 a lot easier to rest during the day so we don't need 714 00:43:48 --> 00:43:50 to waste all the energy [UNINTELLIGIBLE]. 715 00:43:50 --> 00:43:52 PROFESSOR: So another possibility is energy 716 00:43:52 --> 00:43:55 conservation. 717 00:43:55 --> 00:44:02 You could be awake all of the time, but if you can't hunt 718 00:44:02 --> 00:44:11 when it's dark, you might as well go and power down the disk 719 00:44:11 --> 00:44:16 drive or something like that and not use as much energy. 720 00:44:16 --> 00:44:19 Your brain's pretty active while you're asleep, as you may 721 00:44:19 --> 00:44:21 gather from this, but the rest of you, of course, is 722 00:44:21 --> 00:44:23 getting some rest. 723 00:44:23 --> 00:44:25 Anything else? 724 00:44:25 --> 00:44:28 Any other good possibilities? 725 00:44:28 --> 00:44:38 Along with that energy saving one -- we can motivate this one 726 00:44:38 --> 00:44:42 related to energy saving by asking where do you sleep 727 00:44:42 --> 00:44:43 when it gets dark? 728 00:44:43 --> 00:44:46 AUDIENCE: [INAUDIBLE] 729 00:44:46 --> 00:44:47 PROFESSOR: In bed. 730 00:44:47 --> 00:44:47 That's seems like a good place. 731 00:44:47 --> 00:44:49 Where did you put your bed? 732 00:44:49 --> 00:44:55 AUDIENCE: [INAUDIBLE] 733 00:44:55 --> 00:45:00 PROFESSOR: Anybody big on sleeping on, like putting their 734 00:45:00 --> 00:45:02 bed out on the sidewalk? 735 00:45:02 --> 00:45:06 Those of you who are hunter/gatherers, when you're 736 00:45:06 --> 00:45:10 tired you just lie down in the middle of the field? 737 00:45:10 --> 00:45:11 No. 738 00:45:11 --> 00:45:14 Because it's not really very safe. 739 00:45:14 --> 00:45:21 So another possibility is that you want to sleep for purposes 740 00:45:21 --> 00:45:27 of protecting yourself at times that are-- as a corollary of 741 00:45:27 --> 00:45:29 this you can't hunt all day thing. 742 00:45:29 --> 00:45:33 There are other things out there that have adapted 743 00:45:33 --> 00:45:36 themselves to the niche that you are not in. 744 00:45:36 --> 00:45:39 Like take hunt at night, so if you're not going to hunt at 745 00:45:39 --> 00:45:43 night, not only do you want to be calm and quiet, you want to 746 00:45:43 --> 00:45:47 be out of the way, because otherwise oh, look, he's 747 00:45:47 --> 00:45:50 asleep, let's eat him. 748 00:45:50 --> 00:45:52 So there's a sort of a safety aspect to it. 749 00:45:52 --> 00:45:54 The other part of the safety aspect is that not only don't 750 00:45:54 --> 00:45:57 you want to hunt at night, if you just go down wandering 751 00:45:57 --> 00:45:58 around aimlessly at night, you're going to falli in a 752 00:45:58 --> 00:45:59 hole and hurt yourself. 753 00:45:59 --> 00:46:04 So, you've got to get in the hole first and go to sleep. 754 00:46:04 --> 00:46:06 Do I have any other brilliant theories here that I 755 00:46:06 --> 00:46:07 wanted to mention? 756 00:46:07 --> 00:46:08 That's pretty good. 757 00:46:08 --> 00:46:14 You guys managed to do a quick survey of the leading theories. 758 00:46:14 --> 00:46:21 As I say, a lot of the cool, current data centers around 759 00:46:21 --> 00:46:25 this idea of sleep having a role in learning. 760 00:46:25 --> 00:46:28 761 00:46:28 --> 00:46:30 Let me tell you a little bit about that. 762 00:46:30 --> 00:46:34 The picture that's on the handout is an illustration 763 00:46:34 --> 00:46:40 of what looks like a really trivial task. 764 00:46:40 --> 00:46:45 The question is, is there a little vertical region in 765 00:46:45 --> 00:46:47 that display somewhere? 766 00:46:47 --> 00:46:51 The answer is well, yeah. 767 00:46:51 --> 00:46:59 Now I can make that task arbitrarily difficult by 768 00:46:59 --> 00:47:02 flashing the stimulus very briefly and following it 769 00:47:02 --> 00:47:04 with a mask of some sort. 770 00:47:04 --> 00:47:08 So I can make it hard. 771 00:47:08 --> 00:47:11 I can make it as hard as I like. 772 00:47:11 --> 00:47:22 If I do that, what I can do is measure, let's call 773 00:47:22 --> 00:47:29 it a threshold time. 774 00:47:29 --> 00:47:34 So maybe in order for you to get this task correct 70% of 775 00:47:34 --> 00:47:37 the time, I initially need to have the stimulus on 776 00:47:37 --> 00:47:38 for 200 milliseconds. 777 00:47:38 --> 00:47:41 778 00:47:41 --> 00:47:51 If you practice it for a while, you'll get better and that'll 779 00:47:51 --> 00:47:53 level off at some point. 780 00:47:53 --> 00:47:57 What a number of people have -- well, is it 781 00:47:57 --> 00:47:58 Carney and Sagi I think? 782 00:47:58 --> 00:48:02 Doug Sagi is the guy I know. 783 00:48:02 --> 00:48:04 What a number of people found, starting I think with Carney 784 00:48:04 --> 00:48:12 and Sagi, is that if you let people sleep, in particular if 785 00:48:12 --> 00:48:17 they are allowed to have REM sleep, that performance gets -- 786 00:48:17 --> 00:48:19 well, here's let's have him sleep for eight hours here. 787 00:48:19 --> 00:48:22 788 00:48:22 --> 00:48:28 That performance gets better, as if something happened 789 00:48:28 --> 00:48:29 while they were asleep. 790 00:48:29 --> 00:48:33 If they don't sleep during this period they don't get better. 791 00:48:33 --> 00:48:37 So it's a sleep dependent improvement in behavior. 792 00:48:37 --> 00:48:41 This is a very specific little bit of learning. 793 00:48:41 --> 00:48:43 This isn't just a general overall improvement 794 00:48:43 --> 00:48:45 in behavior. 795 00:48:45 --> 00:48:45 If 796 00:48:45 --> 00:48:49 you trained people with that little vertical task, that 797 00:48:49 --> 00:48:52 you're doing a task, is that region vertical or 798 00:48:52 --> 00:48:53 horizontal, right. 799 00:48:53 --> 00:48:54 That the three thing is vertical or the three thing is 800 00:48:54 --> 00:48:58 horizontal right It's always I'm looking here and it's 801 00:48:58 --> 00:49:00 always down and to my left. 802 00:49:00 --> 00:49:04 I learn to be faster here. 803 00:49:04 --> 00:49:07 I don't learn to be faster here. 804 00:49:07 --> 00:49:11 The improvement in learning is specific to the little piece of 805 00:49:11 --> 00:49:14 retina that I have trained. 806 00:49:14 --> 00:49:20 So it's very specific sort of learning that seems to be 807 00:49:20 --> 00:49:25 dependent on getting a decent night's sleep. 808 00:49:25 --> 00:49:31 Now, interestingly, there is evidence -- how many 809 00:49:31 --> 00:49:32 people here are nappers? 810 00:49:32 --> 00:49:35 811 00:49:35 --> 00:49:38 How many people are nappers just because it happens? 812 00:49:38 --> 00:49:42 813 00:49:42 --> 00:49:43 We can do it this way. 814 00:49:43 --> 00:49:47 How many people here think that if they take a nap in the 815 00:49:47 --> 00:49:50 middle of the day, they wake up feeling better for 816 00:49:50 --> 00:49:52 the experience? 817 00:49:52 --> 00:49:57 How many people think if they have a nap they wake up feeling 818 00:49:57 --> 00:49:59 cruddy for the rest of the day? 819 00:49:59 --> 00:50:02 820 00:50:02 --> 00:50:06 There are people who find naps to be refreshing and useful, 821 00:50:06 --> 00:50:09 and there are people who find it being disruptive. 822 00:50:09 --> 00:50:13 It was certainly a big improvement in my professional 823 00:50:13 --> 00:50:15 life when I reached the level where I had an 824 00:50:15 --> 00:50:18 office of my own. 825 00:50:18 --> 00:50:21 The biggest part of that was it made napping a great 826 00:50:21 --> 00:50:24 deal more graceful. 827 00:50:24 --> 00:50:30 After lunch I could take the latest issue of Vision Research 828 00:50:30 --> 00:50:34 and prop it up and stare at the same two sentences for like 829 00:50:34 --> 00:50:37 fifteen minutes and I feel much better thereafter. 830 00:50:37 --> 00:50:41 831 00:50:41 --> 00:50:47 There is evidence that a properly timed nap is just 832 00:50:47 --> 00:50:51 about as good as a night's sleep for this sort of 833 00:50:51 --> 00:50:52 perceptual learning. 834 00:50:52 --> 00:50:54 This is work done by Sara Mednick originally, 835 00:50:54 --> 00:50:58 up at Harvard. 836 00:50:58 --> 00:50:59 This is new stuff. 837 00:50:59 --> 00:51:04 We don't really quite understand fully how 838 00:51:04 --> 00:51:05 far we can take this. 839 00:51:05 --> 00:51:10 It's the sort of thing that your average MIT student is 840 00:51:10 --> 00:51:13 tempted to take and run with, right. 841 00:51:13 --> 00:51:17 Oh man, I can get the whole benefit of eight hours of sleep 842 00:51:17 --> 00:51:22 if I just go for -- I think it's ninety minutes between 843 00:51:22 --> 00:51:24 like 2:00 or 3:00 in the afternoon. 844 00:51:24 --> 00:51:25 That works. 845 00:51:25 --> 00:51:26 Great. 846 00:51:26 --> 00:51:28 Now I can stay up all night. 847 00:51:28 --> 00:51:30 Anyway, we don't know that yet. 848 00:51:30 --> 00:51:34 But Mednick's study is an interesting suggestion that 849 00:51:34 --> 00:51:39 sleep during-- napping sleep can serve as a same sort of 850 00:51:39 --> 00:51:42 perceptual learning kind of role. 851 00:51:42 --> 00:51:50 But look, one might actually wonder whether anybody other 852 00:51:50 --> 00:51:55 than vision researchers cares about whether or not you can 853 00:51:55 --> 00:51:59 find little briefly flashed lines in one corner of 854 00:51:59 --> 00:52:00 your visual field. 855 00:52:00 --> 00:52:03 That's not what you want to know about learning and memory. 856 00:52:03 --> 00:52:06 What you want to know is is anything really useful 857 00:52:06 --> 00:52:08 happening while you're asleep. 858 00:52:08 --> 00:52:12 In particular, one of the things that people want to 859 00:52:12 --> 00:52:18 know is, can you do serious thinking in your sleep? 860 00:52:18 --> 00:52:25 One thing you can't do is study in your sleep. 861 00:52:25 --> 00:52:29 There have been endless efforts because people smelled money at 862 00:52:29 --> 00:52:33 the far end of this to produce like tapes that you could 863 00:52:33 --> 00:52:36 stick under the pillow. 864 00:52:36 --> 00:52:41 Record Gleitman and why waste precious waking 865 00:52:41 --> 00:52:43 hours reading Gleitman? 866 00:52:43 --> 00:52:47 I'll just have somebody else read it to me while I'm asleep. 867 00:52:47 --> 00:52:51 Sorry, the overwhelming evidence is that 868 00:52:51 --> 00:52:53 nothing happens. 869 00:52:53 --> 00:52:59 The mild effects that are sporadically shown here come 870 00:52:59 --> 00:53:02 from periodic awakenings during the night. 871 00:53:02 --> 00:53:06 That also goes for sleeping through the lecture. 872 00:53:06 --> 00:53:08 If you're sound asleep during the lecture it's lovely that 873 00:53:08 --> 00:53:12 you were here, but you'll have to ask somebody else 874 00:53:12 --> 00:53:15 what actually happened. 875 00:53:15 --> 00:53:16 So that doesn't work. 876 00:53:16 --> 00:53:22 But can you have insights, or can you do your problem sets 877 00:53:22 --> 00:53:26 during your sleep in some sense? 878 00:53:26 --> 00:53:29 How many people have had the experience of being sort of 879 00:53:29 --> 00:53:35 dead-ended on a problem, it's time to just give it up, you go 880 00:53:35 --> 00:53:38 to sleep and you wake up and somehow the answer kind 881 00:53:38 --> 00:53:40 of seems to be there? 882 00:53:40 --> 00:53:44 It's a not uncommon experienc and there are lots of anecdotes 883 00:53:44 --> 00:53:46 in the literature about this. 884 00:53:46 --> 00:53:52 One of the famous ones is the guy who first described the 885 00:53:52 --> 00:53:56 ring structure of benzene, claims that he had a dream of a 886 00:53:56 --> 00:53:59 snake biting his tail and he woke up knowing that benzene 887 00:53:59 --> 00:54:01 was a ring or something. 888 00:54:01 --> 00:54:02 It doesn't always work, by the way. 889 00:54:02 --> 00:54:10 My father spent his career as a physicist and had 890 00:54:10 --> 00:54:11 the same experience. 891 00:54:11 --> 00:54:14 He's working on a problem, not getting anywhere. 892 00:54:14 --> 00:54:17 Goes to sleep, wakes up in the middle of the night, he knows 893 00:54:17 --> 00:54:22 the answer, and he knows you don't remember stuff from the 894 00:54:22 --> 00:54:24 middle of the night, so he writes it down fast and 895 00:54:24 --> 00:54:26 goes back to sleep. 896 00:54:26 --> 00:54:29 Gets up the next morning as predicted, has no recollection 897 00:54:29 --> 00:54:32 of what the great answer was, but he doesn't remember writing 898 00:54:32 --> 00:54:34 it down, which is good. 899 00:54:34 --> 00:54:37 So he looks at it and he sees that the answer is, "All the 900 00:54:37 --> 00:54:46 world is fused with the smell of cinnamon," which I'm sure 901 00:54:46 --> 00:54:51 was an answer, but was it necessarily the answer 902 00:54:51 --> 00:54:54 he was looking for. 903 00:54:54 --> 00:55:00 So this notion that you could actually be doing something 904 00:55:00 --> 00:55:07 productive in that sense during sleep was really in the realm 905 00:55:07 --> 00:55:12 of anecdote until this year. 906 00:55:12 --> 00:55:17 I put the reference on the paper by this group in Germany 907 00:55:17 --> 00:55:19 led by -- I suppose since he's in Germany, he must 908 00:55:19 --> 00:55:22 be Wagner et al. 909 00:55:22 --> 00:55:23 Beautiful experiment. 910 00:55:23 --> 00:55:29 You know these number games where you get a string of 911 00:55:29 --> 00:55:33 numbers and you have to predict the next number in the series? 912 00:55:33 --> 00:55:37 Well, I can't remember the particular one here, which is 913 00:55:37 --> 00:55:40 just as well because at MIT all that would happen is if I 914 00:55:40 --> 00:55:42 presented it, you'd be sitting there for the rest of the 915 00:55:42 --> 00:55:44 lecture trying to work out what's the rule here. 916 00:55:44 --> 00:55:47 Anyway, it's a clever -- go look at the paper. 917 00:55:47 --> 00:55:50 It's a beautiful paper. 918 00:55:50 --> 00:55:53 But they picked one of these things where there were 919 00:55:53 --> 00:55:55 two ways to solve it. 920 00:55:55 --> 00:55:59 There is a sort of a laborious multi-step thing. 921 00:55:59 --> 00:56:01 You add the last two numbers and then divide 922 00:56:01 --> 00:56:04 by the third fac number. 923 00:56:04 --> 00:56:05 It's some weird thing. 924 00:56:05 --> 00:56:08 You can do it, but it takes a long time. 925 00:56:08 --> 00:56:14 So, if you measure the amount of time for -- so this is 926 00:56:14 --> 00:56:17 going to be time again. 927 00:56:17 --> 00:56:21 Measure the amount of time to get the answer. 928 00:56:21 --> 00:56:25 People are initially very long and then they get better and to 929 00:56:25 --> 00:56:27 get to some sort of stable. 930 00:56:27 --> 00:56:30 But there's a trick. 931 00:56:30 --> 00:56:34 If you have this flash of insight, you realize I don't 932 00:56:34 --> 00:56:37 remember what, but there's some trivial way of knowing what the 933 00:56:37 --> 00:56:42 number is, and if you get it, it's trivial to see in the data 934 00:56:42 --> 00:56:48 because your time drops like a rock and it stays there. 935 00:56:48 --> 00:56:53 So now what you do is you take people, you train them on this. 936 00:56:53 --> 00:57:01 They're at this the high asymptote here, and 937 00:57:01 --> 00:57:02 you send them away. 938 00:57:02 --> 00:57:07 You either send them away for eight hours of daytime 939 00:57:07 --> 00:57:10 stuff -- come back tonight we'll test you again. 940 00:57:10 --> 00:57:13 You send them away -- I don't remember, do they actually 941 00:57:13 --> 00:57:14 keep them in the lab? 942 00:57:14 --> 00:57:16 You can keep them in the lab and keep them awake. 943 00:57:16 --> 00:57:18 Anyway, you send them away at night because you want to make 944 00:57:18 --> 00:57:20 sure that it's not a day/night thing, but don't 945 00:57:20 --> 00:57:21 let them sleep. 946 00:57:21 --> 00:57:26 Or you have people who go to sleep and have eight 947 00:57:26 --> 00:57:28 hours worth of sleep. 948 00:57:28 --> 00:57:34 The finding is that the next day -- eight hours later rather 949 00:57:34 --> 00:57:42 -- some people are here, some people are here or rapidly get 950 00:57:42 --> 00:57:48 here, and 50% more of the people who had a night's 951 00:57:48 --> 00:57:51 sleep got here. 952 00:57:51 --> 00:57:53 It's not that everybody went to sleep and had 953 00:57:53 --> 00:57:54 this kaboom of insight. 954 00:57:54 --> 00:58:02 But seemingly something about that night sleep produced this 955 00:58:02 --> 00:58:10 rapid burst of insight in many more people in the sleep group 956 00:58:10 --> 00:58:13 than in the two other groups. 957 00:58:13 --> 00:58:17 It's I think the first really good evidence, experimental 958 00:58:17 --> 00:58:28 evidence, for an ability to get something more like higher 959 00:58:28 --> 00:58:32 level cognitive thought happening while you're asleep, 960 00:58:32 --> 00:58:35 Not just these relatively low level perceptual learning 961 00:58:35 --> 00:58:37 kinds of things. 962 00:58:37 --> 00:58:44 So, the general evidence suggests that sleep has an 963 00:58:44 --> 00:58:49 important role to play in managing your cognitive 964 00:58:49 --> 00:58:52 light in some fashion. 965 00:58:52 --> 00:58:56 It probably serves a role in consolidating memory. 966 00:58:56 --> 00:59:02 It probably serves a role in problem solving. 967 00:59:02 --> 00:59:06 It certainly is the sort of thing that one might think 968 00:59:06 --> 00:59:10 about as one is saying I'm going to stay up all night 969 00:59:10 --> 00:59:15 reading Gleitman because tomorrow's the final exam. 970 00:59:15 --> 00:59:17 Well, if you haven't read Gleitman before the final exam 971 00:59:17 --> 00:59:21 it's probably true that reading Gleitman all night is better 972 00:59:21 --> 00:59:24 than hoping that eight hours of sleep will produce a flash of 973 00:59:24 --> 00:59:27 insight about the imagined contents of Gleitman. 974 00:59:27 --> 00:59:31 975 00:59:31 --> 00:59:36 All right, let us discuss -- I'm supposed to tell you what's 976 00:59:36 --> 00:59:39 going to happen when you're sleep deprived I see, but let's 977 00:59:39 --> 00:59:43 do that in a minute after you wake up the person next 978 00:59:43 --> 00:59:46 to you who's dozed off. 979 00:59:46 --> 00:59:47 Because they want to hear this piece. 980 00:59:47 --> 01:03:05 [INTERMISSION IN LECTURE] 981 01:03:05 --> 01:03:05 All right. 982 01:03:05 --> 01:03:10 So what happens to you, you were clearly built to sleep. 983 01:03:10 --> 01:03:15 What happens if you abuse the privilege and you're 984 01:03:15 --> 01:03:17 running a sleep debt? 985 01:03:17 --> 01:03:22 And the answer is most people here, in fact, most people in 986 01:03:22 --> 01:03:25 America are running some sort of a sleep debt. 987 01:03:25 --> 01:03:30 What is the cost? 988 01:03:30 --> 01:03:35 Well, you can measure cost in a variety of different ways. 989 01:03:35 --> 01:03:45 You can certainly measure cost in terms of things like 990 01:03:45 --> 01:03:48 industrial accidents, car crashes and stuff like that. 991 01:03:48 --> 01:03:56 The classic sleep deprivation car crash is a crash on a clear 992 01:03:56 --> 01:04:01 straight road on a moonlit night -- you're a nice long 993 01:04:01 --> 01:04:04 distance trucker who's abusing the rules about how long you're 994 01:04:04 --> 01:04:06 supposed to be able to drive at once. 995 01:04:06 --> 01:04:09 You're out, there's no car in the vicinity, the road is 996 01:04:09 --> 01:04:13 straight, it's not bright light, but you can 997 01:04:13 --> 01:04:14 see everything. 998 01:04:14 --> 01:04:17 The road turns a few degrees and you go straight 999 01:04:17 --> 01:04:19 out into the cactus or something like that. 1000 01:04:19 --> 01:04:23 Because when you get really sleepy, if you take a look at 1001 01:04:23 --> 01:04:26 people's brain waves, you can watch them flipping into these 1002 01:04:26 --> 01:04:31 little micro sleeps that don't necessarily last very long, but 1003 01:04:31 --> 01:04:34 at sixty miles an hour, eighty miles an hour, ninety miles an 1004 01:04:34 --> 01:04:36 hour, they don't need to last very long for you 1005 01:04:36 --> 01:04:41 to end up in sage brush. 1006 01:04:41 --> 01:04:44 There are plenty of ways to measure it in the lab too. 1007 01:04:44 --> 01:04:51 If you sit somebody in the lab and tell them all I want you to 1008 01:04:51 --> 01:04:58 do is push a button when I turn on this little light. 1009 01:04:58 --> 01:05:00 The only thing you need to do. 1010 01:05:00 --> 01:05:05 What you discover is that people are about 200 1011 01:05:05 --> 01:05:11 milliseconds slower at adverse circadian phase, at the bottom 1012 01:05:11 --> 01:05:17 of that circadian trough than they are at the top of it. 1013 01:05:17 --> 01:05:19 And on top that just general slowing. 1014 01:05:19 --> 01:05:21 There are also a whole bunch of times when they'll just 1015 01:05:21 --> 01:05:23 miss the light altogether. 1016 01:05:23 --> 01:05:31 The light will come on and the subject will be just ah and 1017 01:05:31 --> 01:05:32 not do anything about it. 1018 01:05:32 --> 01:05:37 Now, 200 milliseconds, what's the big deal there? 1019 01:05:37 --> 01:05:39 It's only a fifth of a second. 1020 01:05:39 --> 01:05:42 Well, again, at ninety miles an hour it makes a difference 1021 01:05:42 --> 01:05:47 and if you're flying your supersonic jet around the skies 1022 01:05:47 --> 01:05:50 of Iraq or something it makes even more of a difference. 1023 01:05:50 --> 01:05:54 So there's a generalized slowing. 1024 01:05:54 --> 01:06:02 There is a tendency to trade-off speed and accuracy 1025 01:06:02 --> 01:06:06 more than usual in favor of speed. 1026 01:06:06 --> 01:06:11 So people tend, when they're sleepy -- we've actually 1027 01:06:11 --> 01:06:12 done this in our lab. 1028 01:06:12 --> 01:06:15 So if you're doing one of these visual search kinds of things 1029 01:06:15 --> 01:06:17 where you're looking for something exciting like where's 1030 01:06:17 --> 01:06:22 the red vertical line, people, if you go too fast 1031 01:06:22 --> 01:06:23 you make mistakes. 1032 01:06:23 --> 01:06:27 People when they're sleepy tend to be willing to tolerate 1033 01:06:27 --> 01:06:28 higher error rates. 1034 01:06:28 --> 01:06:32 Again, that's the sort of thing that is brought out into the 1035 01:06:32 --> 01:06:38 real world if your error rate goes up by two or three times, 1036 01:06:38 --> 01:06:42 that could be a real problem in doing real world tasks. 1037 01:06:42 --> 01:06:46 It is harder to prove but pretty clear, perhaps 1038 01:06:46 --> 01:06:51 introspectively, that being sleepy makes you stupid. 1039 01:06:51 --> 01:06:54 You just don't think as well. 1040 01:06:54 --> 01:06:57 For a long time it was kind of hard to show any effects of 1041 01:06:57 --> 01:07:01 sleep deprivation because people tended to do things like 1042 01:07:01 --> 01:07:05 ask you to add up columns of numbers, and as long as I smack 1043 01:07:05 --> 01:07:08 you around enough to keep you awake during the task, 1044 01:07:08 --> 01:07:10 you can do that. 1045 01:07:10 --> 01:07:14 But if I ask you to do, I don't know, your problem set when 1046 01:07:14 --> 01:07:17 you're really sleepy, it turns out that the throughput on more 1047 01:07:17 --> 01:07:23 complicated cognitive tasks goes downhill. 1048 01:07:23 --> 01:07:25 You're just not as good at it. 1049 01:07:25 --> 01:07:28 Will it kill you? 1050 01:07:28 --> 01:07:29 How bad can it be? 1051 01:07:29 --> 01:07:32 The answer is probably yes. 1052 01:07:32 --> 01:07:39 Not obviously at the level that people inflict on themselves, 1053 01:07:39 --> 01:07:42 but prolonged sleep deprivation will kill you if you 1054 01:07:42 --> 01:07:45 are a rat, at least. 1055 01:07:45 --> 01:07:49 What kills you is not that you just get so sleepy that you 1056 01:07:49 --> 01:07:55 fall over dead, but that staying awake, or more to the 1057 01:07:55 --> 01:08:00 point being kept awake, which is what's required if you're 1058 01:08:00 --> 01:08:03 going to go any extended period of sleep deprivation, is highly 1059 01:08:03 --> 01:08:08 stressful, and stress will kill you. 1060 01:08:08 --> 01:08:11 The rats who die in sleep deprivation studies 1061 01:08:11 --> 01:08:12 die of things like 1062 01:08:12 --> 01:08:16 bleeding ulcers and stuff like that. 1063 01:08:16 --> 01:08:19 Symptoms that look for all the world like the 1064 01:08:19 --> 01:08:24 effects of severe stress. 1065 01:08:24 --> 01:08:29 You can also ask whether or not deprivation of 1066 01:08:29 --> 01:08:34 particular kinds of sleep is particularly damaging. 1067 01:08:34 --> 01:08:39 So, for example, it's relatively easy to deprive 1068 01:08:39 --> 01:08:41 somebody of REM sleep. 1069 01:08:41 --> 01:08:47 You can just monitor their eye movements or their brain waves 1070 01:08:47 --> 01:08:51 and wake them up every time they go into REM sleep. 1071 01:08:51 --> 01:08:56 They will sleep for most of the night that way, but they'll 1072 01:08:56 --> 01:08:58 have little or no REM. 1073 01:08:58 --> 01:09:01 You do get effects of that on these perceptual learning 1074 01:09:01 --> 01:09:05 tasks -- REM seems to be important in that. 1075 01:09:05 --> 01:09:08 But you can be REM deprived for an extended period of time 1076 01:09:08 --> 01:09:14 without collapsing in a heap. 1077 01:09:14 --> 01:09:15 There are two reasons we know that. 1078 01:09:15 --> 01:09:17 One of them is that people have done experimental 1079 01:09:17 --> 01:09:18 studies of this. 1080 01:09:18 --> 01:09:21 The other is that one class of antidepressants known as 1081 01:09:21 --> 01:09:29 Monoamine Oxidase Inhibitors, MAOIs, systematically suppress 1082 01:09:29 --> 01:09:34 REM sleep, and these patients report that they don't dream. 1083 01:09:34 --> 01:09:37 But they don't have obvious evil side effects. 1084 01:09:37 --> 01:09:41 We don't quite understand how that relates to these theories. 1085 01:09:41 --> 01:09:43 People on these things don't say oh my goodness, I 1086 01:09:43 --> 01:09:44 can't learn anymore. 1087 01:09:44 --> 01:09:47 So there's something we don't understand about the 1088 01:09:47 --> 01:09:50 relationship between REM and learning there, because 1089 01:09:50 --> 01:09:53 otherwise these antidepressants would have a powerful side 1090 01:09:53 --> 01:09:56 effect, cognitive side effect that we don't see. 1091 01:09:56 --> 01:10:00 The other way to do this in animal studies is to keep an 1092 01:10:00 --> 01:10:05 animal REM deprived for a month at a time and see if the animal 1093 01:10:05 --> 01:10:11 show these sort of stress symptoms, and the answer seems 1094 01:10:11 --> 01:10:13 to be, well, no, not really. 1095 01:10:13 --> 01:10:16 If you get sleep, even without REM sleep, the stress 1096 01:10:16 --> 01:10:18 part can not be there. 1097 01:10:18 --> 01:10:23 Oh, my favorite technique for REM depriving a cat in this 1098 01:10:23 --> 01:10:26 case, this is a low REM -- if you want to REM deprive your 1099 01:10:26 --> 01:10:29 cat, here's how you do it. 1100 01:10:29 --> 01:10:34 You put the cat -- take a flower pot, turn the flower pot 1101 01:10:34 --> 01:10:37 upside-down, put the cat on the flower pot in the middle of 1102 01:10:37 --> 01:10:40 a little artificial lake. 1103 01:10:40 --> 01:10:45 Eventually the cat goes to sleep, right. 1104 01:10:45 --> 01:10:49 Then the cat falls into REM sleep. 1105 01:10:49 --> 01:10:52 Falls off into the water. 1106 01:10:52 --> 01:10:54 Cat doesn't like to fall into the water. 1107 01:10:54 --> 01:10:57 Cat wakes up. 1108 01:10:57 --> 01:11:05 And the cats learns the not go into REM sleep. 1109 01:11:05 --> 01:11:09 In some sense, trains itself not to fall into REM sleep, 1110 01:11:09 --> 01:11:12 with the result that you can REM deprive the cat for an 1111 01:11:12 --> 01:11:14 extended period of time. 1112 01:11:14 --> 01:11:15 This is a very weird study. 1113 01:11:15 --> 01:11:18 I don't where they got their measures. 1114 01:11:18 --> 01:11:20 The only thing I can remember that the only thing they found 1115 01:11:20 --> 01:11:25 that was unusual about this cat is that a normal cat, you got 1116 01:11:25 --> 01:11:30 the cat food, if you put a July the 4th kind of sparkler in the 1117 01:11:30 --> 01:11:34 cat food, a normal cat will not eat the the cat food, but 1118 01:11:34 --> 01:11:36 a REM deprived cat will. 1119 01:11:36 --> 01:11:39 Why? 1120 01:11:39 --> 01:11:39 I don't know. 1121 01:11:39 --> 01:11:41 I don't know nothing about this. 1122 01:11:41 --> 01:11:46 I only know what I read in the literature. 1123 01:11:46 --> 01:11:49 Which reminds me, however -- actually, this should 1124 01:11:49 --> 01:11:51 have reminded me. 1125 01:11:51 --> 01:11:53 That the most practical piece of advice, apart from the 1126 01:11:53 --> 01:11:57 fact you should get eight hours of sleep at night. 1127 01:11:57 --> 01:12:01 Since you won't get eight hours of sleep a night, I notice, 1128 01:12:01 --> 01:12:04 I've been lecturing to this course for twenty plus years, 1129 01:12:04 --> 01:12:10 and in spite of my exortations that your physical and 1130 01:12:10 --> 01:12:13 cognitive well-being really relies on you going to sleep at 1131 01:12:13 --> 01:12:15 night, none of you are going to pay the slightest bit 1132 01:12:15 --> 01:12:16 of attention to that. 1133 01:12:16 --> 01:12:18 So the more practical piece of advice I can give you 1134 01:12:18 --> 01:12:20 is how to sleep in class. 1135 01:12:20 --> 01:12:22 1136 01:12:22 --> 01:12:26 The trick is -- I mean obviously what you want to do 1137 01:12:26 --> 01:12:33 is you want to sleep in a way that kind of masks that fact. 1138 01:12:33 --> 01:12:36 The difficulty is this REM sleep business. 1139 01:12:36 --> 01:12:39 1140 01:12:39 --> 01:12:47 The problem is the muscle tone thing and it's the head bob 1141 01:12:47 --> 01:12:55 portion of the-- So I can look out there and watch the 1142 01:12:55 --> 01:13:03 whiplash and that's not going to work. 1143 01:13:03 --> 01:13:09 So, what people figure out on their own is that what you want 1144 01:13:09 --> 01:13:14 to do is you want to give the illusion that what I or 1145 01:13:14 --> 01:13:19 somebody else is saying is so deep that you had to close your 1146 01:13:19 --> 01:13:21 eyes to think about it. 1147 01:13:21 --> 01:13:25 Now, there are a couple of important principles here. 1148 01:13:25 --> 01:13:32 One of them is that it's less convincing that you're 1149 01:13:32 --> 01:13:37 thinking deeply about this if your mouth falls open. 1150 01:13:37 --> 01:13:41 If you're drooling it's really bad. 1151 01:13:41 --> 01:13:45 This is good. 1152 01:13:45 --> 01:13:47 Support for the chin is good. 1153 01:13:47 --> 01:13:53 The other thing that you learned in like 801 was that 1154 01:13:53 --> 01:13:55 three-legged stools stand better than two-legged 1155 01:13:55 --> 01:13:56 ones, right? 1156 01:13:56 --> 01:13:57 So, I favor these. 1157 01:13:57 --> 01:14:01 1158 01:14:01 --> 01:14:06 I'm really thinking very hard about what you're saying. 1159 01:14:06 --> 01:14:07 That can actually be quite -- in fact, you're 1160 01:14:07 --> 01:14:08 not fooling anybody. 1161 01:14:08 --> 01:14:11 You know perfectly well you're sound asleep. 1162 01:14:11 --> 01:14:12 What? 1163 01:14:12 --> 01:14:14 AUDIENCE: [INAUDIBLE] 1164 01:14:14 --> 01:14:16 PROFESSOR: Oh, keeping the airway open is good. 1165 01:14:16 --> 01:14:23 That was the winner of the most embarrassing moment in Intro 1166 01:14:23 --> 01:14:27 Psych Student Experience. 1167 01:14:27 --> 01:14:30 This was actually the first year I was teaching the course. 1168 01:14:30 --> 01:14:35 I was co-teaching it with another guy in course nine at 1169 01:14:35 --> 01:14:39 the time and he was lecturing. 1170 01:14:39 --> 01:14:41 I've long ago stopped figuring that this was an editorial 1171 01:14:41 --> 01:14:42 comment when people fall asleep. 1172 01:14:42 --> 01:14:45 But anyway, somebody sitting right about over there 1173 01:14:45 --> 01:14:48 fell sound asleep. 1174 01:14:48 --> 01:14:52 But nobody was sitting next to them. 1175 01:14:52 --> 01:14:56 They fell sound asleep and they started to snore. 1176 01:14:56 --> 01:15:02 Eventually this got like loud enough that my colleague had 1177 01:15:02 --> 01:15:04 to say somebody's going. 1178 01:15:04 --> 01:15:07 If you want the definition of embarrassed -- the definition 1179 01:15:07 --> 01:15:10 of embarrassed is you're sitting in lecture, everybody's 1180 01:15:10 --> 01:15:18 looking at you and you have no idea why. 1181 01:15:18 --> 01:15:21 So, sitting next to somebody's another good strategy if you're 1182 01:15:21 --> 01:15:22 actually trying to stay more or less alert. 1183 01:15:22 --> 01:15:28 My old doctoral advisor and I had this as a pact when I was 1184 01:15:28 --> 01:15:32 in graduate school during the Friday afternoon, terrible 1185 01:15:32 --> 01:15:34 time, departmental colloquia. 1186 01:15:34 --> 01:15:37 We would sit next to each other and if it was actually talk 1187 01:15:37 --> 01:15:42 that we cared about, we had an agreement, if I go out, poke 1188 01:15:42 --> 01:15:43 me, because I kind of want to know what this guy 1189 01:15:43 --> 01:15:44 is talking about. 1190 01:15:44 --> 01:15:47 He was department chair. 1191 01:15:47 --> 01:15:49 Turns out to be very important, because one of the rules of 1192 01:15:49 --> 01:15:53 you're department chair is you have to be able to ask an 1193 01:15:53 --> 01:15:55 intelligent question at the end of the talk. 1194 01:15:55 --> 01:15:57 Really good department chairs can do that after sleeping 1195 01:15:57 --> 01:15:59 through the talk. 1196 01:15:59 --> 01:16:03 My advisor, who was otherwise an exemplary department chair, 1197 01:16:03 --> 01:16:08 was caught up short on this at one talk where he asked a very 1198 01:16:08 --> 01:16:11 good question, but one that he wouldn't have asked had he been 1199 01:16:11 --> 01:16:14 awake for those twenty minutes of the talk. 1200 01:16:14 --> 01:16:17 Because the guy had discussed this matter extensively. 1201 01:16:17 --> 01:16:21 So if we would poke each other to stay awake. 1202 01:16:21 --> 01:16:25 The guy joined our lab and he sat two seats away from me. 1203 01:16:25 --> 01:16:27 He went out cold. 1204 01:16:27 --> 01:16:29 That's OK. 1205 01:16:29 --> 01:16:30 But he started shouting. 1206 01:16:30 --> 01:16:35 In Japanese. 1207 01:16:35 --> 01:16:36 Actually, it was probably a 1208 01:16:36 --> 01:16:38 bonus that it was in Japanese because whatever he was 1209 01:16:38 --> 01:16:42 shouting was incomprehensible to anybody else. 1210 01:16:42 --> 01:16:46 I made this sort of dramatic lunge to get to him before 1211 01:16:46 --> 01:16:48 he could manage to get out too much. 1212 01:16:48 --> 01:16:53 1213 01:16:53 --> 01:16:56 So now if you're worried about that, you kind of want to be 1214 01:16:56 --> 01:16:59 sitting with your friends here so that when you start talking 1215 01:16:59 --> 01:17:03 in your sleep, somebody can get to you before it becomes 1216 01:17:03 --> 01:17:05 really desperately obvious. 1217 01:17:05 --> 01:17:06 All right. 1218 01:17:06 --> 01:17:13 I suppose the bottom line is that sleep deprivation will 1219 01:17:13 --> 01:17:18 not kill you, but it won't do anything good for you, 1220 01:17:18 --> 01:17:21 except perhaps getting you through the your work. 1221 01:17:21 --> 01:17:28 Now, let's see do I want to -- you know this looks like a 1222 01:17:28 --> 01:17:33 pretty good place to entertain questions and we'll go on to 1223 01:17:33 --> 01:17:36 dreaming after Thanksgiving. 1224 01:17:36 --> 01:17:39 Any sleep questions while we're here? 1225 01:17:39 --> 01:17:42 1226 01:17:42 --> 01:17:44 We got a question, then you can run for it. 1227 01:17:44 --> 01:17:52 AUDIENCE: [INAUDIBLE] 1228 01:17:52 --> 01:17:56 PROFESSOR: Well, the piece of that is right -- so the 1229 01:17:56 --> 01:17:59 question is do you want to sleeps in cycles of 1230 01:17:59 --> 01:18:00 ninety minutes? 1231 01:18:00 --> 01:18:02 Ideally, you want to wake up on your own. 1232 01:18:02 --> 01:18:06 Typically out of the end of a REM stage is what 1233 01:18:06 --> 01:18:09 would normally happen. 1234 01:18:09 --> 01:18:11 Yes, you will tend to feel more refreshed there than 1235 01:18:11 --> 01:18:13 if you wake up out of this. 1236 01:18:13 --> 01:18:20 But most of us wake up when the alarm clock goes off and sorry. 1237 01:18:20 --> 01:18:20 But if 1238 01:18:20 --> 01:18:23 you can manage to adjust that to wake you up -- even if you 1239 01:18:23 --> 01:18:25 have to move it a little earlier, you may feel better 1240 01:18:25 --> 01:18:29 if you're waking yourself up out of a REM state. 1241 01:18:29 --> 01:18:29 Yup? 1242 01:18:29 --> 01:18:32 1243 01:18:32 --> 01:18:35 AUDIENCE: [INAUDIBLE] 1244 01:18:35 --> 01:18:39 PROFESSOR: Oh, that's the neck floppy thing. 1245 01:18:39 --> 01:18:43 When your muscles are going, when you're losing muscle tone 1246 01:18:43 --> 01:18:48 and drifting off into a REM state, bits of you are kind of 1247 01:18:48 --> 01:18:52 going where gravity wants to go and that can feel like a 1248 01:18:52 --> 01:18:55 falling sensation, which inconveniently can sometimes 1249 01:18:55 --> 01:18:57 lurch you back awake, or conveniently if you happen to 1250 01:18:57 --> 01:19:00 be going out during class. 1251 01:19:00 --> 01:19:04 But I think that's typically an effect of the losing 1252 01:19:04 --> 01:19:05 muscle tone part. 1253 01:19:05 --> 01:19:08 1254 01:19:08 --> 01:19:09 Last chance, here we go. 1255 01:19:09 --> 01:19:16 AUDIENCE: [INAUDIBLE] 1256 01:19:16 --> 01:19:18 PROFESSOR: Oh, if you really live in really, really northern 1257 01:19:18 --> 01:19:23 -- sleep disorders go up as latitude goes up or way down. 1258 01:19:23 --> 01:19:27 But as long as you're living someplace where the sun comes 1259 01:19:27 --> 01:19:29 up every day, that's not an issue. 1260 01:19:29 --> 01:19:32 But yes, absolutely, if you go and live someplace where it's 1261 01:19:32 --> 01:19:37 dark for six months of the year, people have disruptions 1262 01:19:37 --> 01:19:41 of their circadian clock and they start free-running. 1263 01:19:41 --> 01:19:42 All right. 1264 01:19:42 --> 01:19:43 Drive carefully. 1265 01:19:43 --> 01:19:45 Have a good vacation. 1266 01:19:45 --> 01:19:47